Solar cars

http://www.pspb.org/e21/media/MS_S05_Andy_Lau.ppt

Materials - 5 water bottle caps, pop caps or film canister caps - 1 wire hanger or similar piece of hard straight wire - 1 plastic straw - 1 small or medium elastic band - 2 solar cells (sometimes the cell will already come with wires and a motor) - 1 small 1 1/2 volt motor or a similar one (make sure that the motor has a small pulley, if not you will have to get one) - A small wire to connect the solar cells to the motor ( may be included with the motor and/or cell when you buy it...if not you will need to get one) - 1 rectangular piece of thin wood-board or a piece of cardboard (e.g. pizza box) about 7 X 20cm (2 1/2 X 8 inches) - tape - glue or hot glue gun - sun

Suggested List of Tools - 1 pair of pliers - 1 small pointy screw (it will be used to make holes in the caps) - 1 pair of scissors - Hot glue gun (optional) - screw driver - ruler - pen or pencil

How To Assemble

	The Wheels 4 of the caps will be used as wheels. Drill a hole in the center of all the caps just big enough to pass the wire through. It is important to be in the center as much as possible. The Pulley 1 cap will be used as a pulley. Using a pair of scissors, remove the part of the cap that screws onto the bottle, leaving only the top flat part. The inside part of the cap is designed with a small inner wall to hug the bottle rim to give it a tight fit and prevent leaks, this inner wall will serve as the support for the pulley. Please note that not all caps are made the same or may not contain the rim. In this case you may want to use a film canister top instead of a bottle cap.
	Building the Driving Wheel Glue one cap and the pulley together, make sure that the holes are aligned and make sure that the higher part of the pulley is on the outside, creating a groove in the middle. Axles Cut 2 pieces of wire about 12cm long (4 1/2 inches), make sure that they are straight. Cut 4 pieces of straw about 2 1/2cms (1 inch). Slide 2 pieces of straw onto each wire. Place the driving wheel on one end of a piece of wire (the open part of the cap facing outside). Add the other caps on to the end of the wires, all with the open part facing outside. Glue the caps on to the ends of the wires (make sure that they are all centered otherwise your car will wiggle and may not drive straight). You may want to do one at a time and let the glue dry before doing the other wheels (be patient).
	The Base or Chassis Place each axle about 1 1/2cm (> 1/2 inch) from each end of the thin wood board (or cardboard). Use a piece of tape (over the wire) to hold the axle in place while you adjust its position. Once you have it in place use another piece of tape, this time over the straw. Adjust the space between the straw and the wheel in a way to prevent the wheels from moving too much and keep it centered as much as possible. Once positioned properly, tape the straws in place to the wood-board or cardboard.
	The Motor The motor will be connected to the driving wheel with the elastic band, so position the motor on the wood-board or cardboard (close to the driving wheel) in a way to keep the elastic band stretched from the driving wheel to the motor (not too much not too little) and straight with the pulley. Mark the place with a pen or pencil. To secure the motor in place you may want to build some sort of support instead of gluing it permanently to the base. This way you can use the same motor again for another solar car or future project. Use 2 small pieces of wood or a small folded strip of cardboard and glue them on each side of the motor. Once the glue is dry all you will need to secure the motor in place is a small piece of tape going across it which will anchor it to the cars chassis.
	The Solar Cells Connect the solar cells together, the positive of one cell to the negative of the other cell. Use either a thin strip of metal (connectors) or use a piece of small wire. Tape the back of the cell together to secure them. You may want to build a support for the cells to secure them in place and keep them from sliding off the car. The support can be built by using a piece of hard wire, similar to a hanger, laid across the chassis (preferably use an aluminum wire as it is lighter).
	Final Step Connect the cells to the motor by using small wires. To reverse the direction that the motor will turn just switch the connection around. Add the elastic band between the driving wheel and the motor, and Presto!
	Congratulations! You just finished building a mini green machine.
	Running the Solar Car Take your car outside, to a flat smooth surface with lots of sun and have fun (preferably to a park and not on the street). Don't forget to name your car, we called ours xof1 (the short form of "The Power of One"). If you want to see other cool solar cars check out our "Links" for links to colleges, universities and even private teams that are building solar cars (it may be a team in your area). The solar car team members are friendly and are always eager to help a fellow solar car enthusiast, and who knows, you may even join one of them in the future. Also visit About Us - "Team" to meet all the nice people on our team.
	Explore Get your friends involved too and have a friendly competition. Whose car goes the fastest and why? Add more cells. What happens? Add the cells in parallel (negative to negative and positive to positive). What happens? Try adding or removing weight to and from the car. How fast does it move? Try modifying the design of the car (axles closer together in the center or towards one end). Is it less stable? Why? What happens if you change the size of the wheels? Does it lose power? Does it go faster?

Materials Checklist:
Solar cars may be propelled using a pulley/ rubber band method or some types of interlocking gears.

1. Solar Cell
2. DC motor
3. Rear Slicks 38mm diameter x 15mm wide (12mm wide for geared slicks)
4. Front Wheels 35mm diameter
5. 3mm dowel for axles
6. Traction Bands (for non-geared slicks)
7. Eyelets or washers
8. Straw
9. Wood Sheet 125 x 50 x 4mm (or larger, so you can cut to any size)
10. Basswood 5mm x 5mm x 20cm stick
11. Motor Mount (With straps if needed)
12. Procedure Sheet

Propulsion Systems:
Propulsion systems include using a solar cell and toy motor with a:

• gear drive
• Pulley and Rubber band drive

Advanced students are encouraged to experiment with different size pulleys, and gears if available.
Basic Tools Required
These items may be required to build the solar vehicle: (You can make your solar car model without them as well)

• craft knife, used to cut or trim soft wood.
• White glue, wood glue or glue gun
• Soldering Iron, needed if you need to solder wires.
• Pliers, used to connect and twist wires together if needed
• rulers, used for measurements
• Pencil, used for marking

Safety Recommendations
During the construction of the solar vehicle, the following safety precautions should be observed.

• Wear safety glasses
• Use care with sharp cutting blades
• Avoid touching the tip of the glue gun or soldering gun
• Put safety first

Standard Assembly Steps
Make your solar car model in 3 simple steps.

Step 1:

Construct the basic car chassis with 4 wheels

Cut a strip of wood that is (5cm) wide. Mark the location of axles by drawing two lines, one on each end of the car, parallel to the front or back side. On the axle lines, mark two points that are (6mm) away from each side. Insert one eye screw in each of the points.

Eye screws are used to hold the axles. Insert the axle and make sure it is level and it can spin freely. If necessary, adjust the eye screws.

Cut some plastic tubes or straws and use them as the spacer in both sides.

Insert the wheels. Wheels may be inserted while the axle is in position.

You can also insert the axle into one wheel and then pass it through the eye screws.

At the end your simple car will look like this. You can use it the way it is or you can turn it over as shown in the picture bellow.

In the model shown here, the gears are built in the rear slicks (rear wheels). With plain wheels, you had to insert a pulley or gear in the same axle with one wheel. If you don't need to install pulleys or gears, continue with step 2.

To mount a pulley or gear next to one wheel, it is a good idea to cut some space for that on your chassis; otherwise, one wheel will stand out and your model will not have a symmetrical shape. The size of this space may vary depending on the size of your pulley or gear. (10mm x 37mm cut is shown in this example)

This is how a pulley or gear may be mounted beside one of the wheels. The pulley or gear must have a hole matching the axle diameter and must feet snugly. Some pulleys and gears require a plastic insert and some drilling in order to adapt the diameter of the axle you are using.

After mounting, make sure that the wheels can spin freely. If necessary, mount a metal washer between the spacer and eye screws.

Other methods of mounting the axle

You may not have eye screws for mounting the axles. This is an alternate method for mounting wheels and axle. Insert the axle in one wheel, slide a washer onto it. Insert a 137mm straw over it and finally insert another washer and another wheel.

Your final wheels and axle will look like this. Hold the straw and spin the wheels. Make sure the wheels can spin freely. If necessary, make some adjustments.

Cut 4 pieces of (5cm) long wood strips and glue them about (5mm) apart where you want to mount the axles.

Insert the axle in the space between the strips and secure them in place using some glue. Cover it with a strip of cardboard or heavy construction paper.

Note that the glue will touch the straw, not the axle. This is how the bottom of your car will look like after covering the axle holder with a strip of paper.

Step 2:

Mount the motor

Insert the small gear or pulley onto the motor's shaft. Place the motor on the self adhesive motor mount and strap it securely and snugly.

Place the motor on the car while the car is on a flat surface. Move it towards the gears until the gears engage. Mark the location of the motor. Avoid too much pressure on the gears because it will increase the friction and make it difficult for the car to move.

If you use pulleys to transmit force, motor must be mounted away from the pulley so that the rubber belt is slightly stretched. Carefully peal off the protective cover of the adhesive pad. Make sure you will not remove the adhesive pad itself. Place the motor where you already marked. Push it down firmly to stick in place.

Step 3:

Mount the solar panel

Place the solar panel on the car. Connect the solar panel to the motor (if they are not already connected).

The solar panel may be mounted horizontally or slanted. It may be secured in place using a few pieces of clear tape. Take the car outside in a sunny location and test it. Does the motor run while you have the car in your hand? Do the wheels spin? Now place the car on a smooth flat surface so that the solar panel is faced to the sun. Does it run on the ground?

You can test your car indoor by replacing the sunlight with a strong portable light you may buy from a hardware store. Just position the lamp about 60cm above the car and see how it works. For best results the portable lamp must have at least a 120 Watt bulb and a reflector. The final solar car you make may be different based on the materials you use, the design implementation and additional decorations you may add.

Decoration may include wooden or cardboard pieces you can add or paints you may use.

Alternate Assembly Procedure for gear driven solar car
The following steps relate to the construction of the basic solar racer vehicle. Steps relating to the completion of the propulsion systems are left to the student's discretion.

Make sure your kit contains the items listed. Locate the grid planning sheet in the kit. Using a pencil and ruler, design the body of the vehicle and propulsion system. Remember, the lighter the vehicle's body, the further it will travel. Show the drawing to the teacher when ready. Locate the balsawood sheet from the kit Transfer the vehicle body pattern to the balsawood. Using the craft knife and straight-edge, carefully cut out the vehicle body.

1. Locate the straw from the kit. Also get scissors and glue gun.
2. Cut straw in half
3. Using the glue gun, attach the straws to the bottom of vehicle, one at each end (parallel to the end)
4. Locate the axles through each straw.
5. Push one wheel into each axle.
6. Insert and axle through each straw.
7. Carefully place the remaining wheel onto each axle.
   Note: This completes construction of the basic solar vehicle.
8. Locate the solar cell Panel and the required parts for the propulsion system chosen gears, pulleys, propeller, or rubber band. (Gears are supplied, Pulleys and propellers are optional.
9. Assemble and attach the propulsion system as designed.
10. Finish your solar racer as desired using paint, markers, etc.
11. Race the assembled vehicle on a flat surface in a sunny day.